Recently, there has developed a demand for remote meter register installations, where the meter register is mounted in some different place than the meter whose reading is registered. Such demand has come for a variety of reasons, including inaccessibility of the meter location for readings to be taken from the meter register, for reasons of appearance of uniformity of installation, so as to cluster a plurality of meters -- eg. electricity, water or gas meter registers -- from a plurality of apartments or other users in a single reading station, etc. In fields such as domestic users of electricity, water or gas for example, the rate of use may be very low, and the rate of rotation of even the lowest reading dial on a meter register may be extremely slow. When the drive of the lower reading dial on a meter register is totally mechanical, as in the basic meter where the meter may be driven from a disc, gear train or otherwise, the actual rate of drive can be compensated by using accurately cut gears, properly mounted in good bearings. However, in any remote meter register, there is not usually a direct mechanical drive for that register. Rather, the remote reading register is often electrically connected to the basic meter, and its lowest reading dial may be driven in step-fashion, one dial division at a time, at the same rate as the lowest reading dial on the basic meter. Thus, it may very often be desirable to provide a remote reading meter register which can be driven in step fashion at the same rate of meter divisions per unit time as the basic meter whose reading it registers.
In a meter such as an electric watt-hour meter, the driving torque which drives the lowest reading dial on the meter register of such meter is usually very low, and the driving rate may be very slow. In the usual circumstance where a remote reading meter register is electrically connected to the meter, the remote reading meter register is made to operate and to register the meter reading by driving the lowest reading dial on the remote register in a stepwise fashion. In other words, each time the lowest reading dial on the meter passes through another dial division, a signal is sent from the meter to the remote reading meter register to step the lowest reading dial on the remote register another dial division. Thus, the remote reading dial is never more than slightly less than one dial division of its lowest reading dial from accurately registering the reading on the transmitter or basic meter. It has been usual to provide a switching arrangement in the transmitting meter, associated with the lowest reading dial, to send reverse polarity DC pulses to the remote reading meter register each time the dial pointer on the transmitting meter passes through one dial division. The switch means which are usually mounted with the transmitting meter are low power, short throw switches requiring a minimum of driving torque; and they are electrically connected with a DC source to send DC signals whose polarity reverses in each subsequent dial position, so as to drive a stepping motor which is associated with the lowest reading dial of the remote reading register.
It has been found, however, that at very low driving speeds of the lowest reading dial, conventional switches are not suitable because they exhibit dead-break or teasing characteristics. In a conventional switch which requires a snap-action or over-centre action to cause the switch to change its throw position, when the plunger is moving very slowly, there is a time period when one contact of the switch lets go from its co-operating contact but does not yet move away from its immediate area. There is, therefore, a non-contact immediately before the switch plunger reaches the operating point during its own operation. Such non-contact is detrimental to the life and electrical performance of the switch, particularly because when there is a very thin insulating boundary of air between the two contacts, arcing may occur between them, even at very low voltages. Further, during the period of non-contact -- which because of the non-operating characteristic of the very slow moving switch plunger is known as a "dead-break" of the spring action of the switch -- there may be a possibility that the switch continuously tries to reclose or otherwise vibrates in the non-contact area or band, and such action is known as "teasing". For example, in the sort of switch which is known commercially as a "micro-switch," where a plunger travels 0.001 inches in 8 hours -- as it might have to do in very low consumption use where the switch is mechanically connected to the lowest reading dial of a meter register -- and where the switch has a dead-break of 0.00005 inches, it would take 24 minutes for the switch plunger to travel through the dead-break. During that time, considerable teasing may occur, with consequent damage to the contacts of the switch.
Thus, it is desirable to provide a "tease-proof" switch which can be operated at very low driving torque and which has no dead-break. Such a switch is, as noted, particularly useful in such systems having remote reading meter registers for watt-hour, gas or water consumption registrations; and may also be useful in clock movements or other rotary, remotely driven or pulsed registration systems. The present invention provides a rotary multiple contact switch which can be particularly adapted as a single-pole, double-throw switch and easily mounted behind the lowest reading dial of a conventional meter register for electrical connection with a remote reading register, either directly or indirectly through an interface of telephone lines, radio transmission, etc. The rotary switch which is provided by this invention particularly includes a rotary staff -- which is the staff on which the dial pointer of the lowest reading dial of the transmitting meter is also mounted -- and to which is physically and electrically secured an electrically conductive, flexible and elongated armature. The armature is mounted to rotate with the staff, and as it rotates it sweeps an area surrounding the staff. Near the outer boundary of the area which the armature sweeps there is mounted a plurality of pins which are electrically insulated one from another, but which may be electrically connected by back connections into two or more groups of pins so as to provide the appropriate switch action. In particular, a plurality of pins can be mounted radially spaced from the rotating staff having two groups which are electrically connected, every second one of the pins in one group and the intervening pins in the other group, to provide the double-throw action of the rotary switch, as described hereafter. The single-pole switch is, of course, provided by the electrical connection from the staff to any one of the pins, and the armature is mounted so as to contact only one pin at a time, as discussed in greater detail hereafter.
The armature of the multiple contact rotary switch according to this invention is, as noted, electrically conductive and flexible. Essentially, the armature is formed of a sheet of suitable material such as berylium copper alloy, or other conductive and flexible material having spring characteristics. As the armature rotates with the staff and sweeps an area around the staff, the outer end of the armature contacts, seriatim, the pins which are radially spaced from the staff. The length of the armature is such that only one pin is contacted at any one time; and the spring characteristic of the material is such as to assure that there is no dead-break in the rotary switch of the present invention, even if its rotary speed is extremely slow.
In the preferred embodiment of the present invention, the armature of the switch is bifurcated at its outer end to have two sections of unequal length. The width of each of the two sections of unequal length may be equal, or they may be unequal. The length of the shorter of the two sections of the bifurcated end of the armature is such as to assure contact of that shorter section with any one of the pins as the armature rotates. During that action, at some time the shorter of the two sections of the bifurcated outer end of the armature loses contact with the pin across which it is wiping an electrical contact, and when that happens the shorter section of the bifurcated outer end of the armature tends to straighten out because of the spring characteristic of the material from which the armature is formed. In so doing, the shorter section of the bifurcated end of the armature thereby springs forward in the rotative direction of the armature, and that action forces the longer of the two sections to lose contact with the pin and also to spring forward to contact the next pin. Thus, a wiping action across the pin is assured, and at the same time there is no dead-break because the spring action of the armature itself assures that once the shorter section of the bifurcated end of the armature has lost contact with a pin with which it was formerly in contact, the longer section is also forced to lose contact and to move forward to make contact with the next pin.
In an alternative embodiment, the armature comprises a single arm which is arranged to wipe across each pin in turn, and which has suitable spring characteristics to assure that the outer end of the arm moves forward to contact the next pin when it loses contact with any pin.
At very low rotative speeds of the switch, the outer end or ends of the armature may move in minute but discrete movements across any pin, in wiping contact therewith. Thus, as the switch shaft rotates very slowly, the armature -- which, as noted, is a light spring -- may hold in frictional contact with the pin for a period of time, and then move across the pin a very short distance under spring force so as to normalize its position. Several such discrete movements may occur before the armature, or one portion of a bifurcated armature, loses contact with the pin and the armature moves forward to the next pin. In any event, there is no teasing because there is no plunger action, and therefore there is no physical placing of the switch components in a position where a dead-break could occur. Also, the spring characteristic of the armature is such as to assure contact of the outer end of the armature in the forward direction of the rotation thereof with one of the pins with which it is intended to contact.